Neuromuscular Diseases and Muscle Relaxant Management

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Neuromuscular Diseases and Muscle Relaxant
Management

• Mark Welliver CRNA, MS
• Assistant Professor
• Florida International University
• School of Nurse Anesthesiology

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NEUROMUSCULAR JUNCTION

• Anatomy

Function
To conduct propagated impulses to the muscle cell
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MOTOR END-PLATE POTENTIAL
?5 protein sub units 2 alpha,beta,delta,gamma
? ACh bound to 2 alpha sub units opens ion
channels
? K out, Na and Ca in
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MUSCLE RELAXANTS

• Depolarizers- PRODUCE NO FADE ON TOF
• Succinylcholine (SCh)- 2 Ach molecules
• Decamethonium- 8 Carbon ammonium chain
• Non- Depolarizers(NDMR) -PRODUCE FADE ON TOF
• Pancuronium, Rocuronium, Vecuronium, Curare...

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NERVE STIMULATOR / MONITORING

• Single Twitch 0.1-0.15 Hz
• Train of Four 2Hz 2 sec.s (0.5 sec.s apart)
• Tetanus 50Hz and 100Hz 5 sec.s
• Double Burst Stimulation(DBS) 50 Hz (750 ms
  apart) 2 sets of 3 bursts appear as two
  twitches
• PURPOSE To evaluate degree of muscle paralysis
  or recovery from paralysis

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NERVE FUNCTION EVALUATION

• Test Receptors Occupied
• Normal Tidal Vol. 80
• Holds Tetanus 50Hz 75-80
• TOF, DBS 75-80
• Holds Tetanus 100Hz 50
• Head lift x 5sec.s 33
• MAY BE occupied by NDMR muscle
  relaxants

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Disease Topics

• Myasthenia Gravis
• Cholinergic Crisis
• Myasthenic Syndrome (Eaton Lambert Disease)
• Muscular Dystrophies
• Myotonias
• Multiple Sclerosis
• Guillain-Barre (Acute Idiopathic Polyneuitis)
• Amyotrophic Lateral Sclerosis (ALS)
• Spinal Cord Injuries
• Burn Patients
• Parkinsons Disease

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Myasthenia Gravis

• POST-Junctional alteration
• Auto-immune response to ACh receptors.(?receptors
  ).
• Onset pharyngeal and ocular weakness.
• Worsens with exercise
• Treatment-anticholinesterases (Edrophonium)
• Under treatment weakness(MYASTHENIC CRISIS)
• Slight resistance to SCh
• Very sensitive to NDMR

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Cholinergic Crisis

• Due to excessive administration of
  anti-cholinesterase drugs. (usually
  Pyridostigmine, 4 hr. duration)
• Signs and Symptoms increasing weakness and
  muscarinic effects

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Myasthenic Crisis vs Cholinergic Crisis

• How to differentiate between Myasthenic Crisis
  and Cholinergic Crisis
  
  GIVE Edrophonium(anti
  cholinesterase) 1-10mg IV ImprovementMyasthe
  nic crisis WorseningCholinergic
  crisis

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Myasthenic Syndrome/Eaton-Lambert Syndrome

• PRE-Junctional alteration
• Decreased ACh release
• Associated with underlying malignancy
  (particularly lung oat cell CA)
• Peripheral and pelvic muscles affected
• Improves with exercise
• Do not improve with anticholinesterases
• Sensitive to NDMR and Depolarizers
  

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Muscular Dystrophy

• Defect of Muscle Fiber (Duchenes most prevalent)
  
• Progressive weakness
• SCh- BAD!, Hyperkalemia, Malignant Hyperthermia
• NDMR- hypersensitive

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Myotonias

• Defect of Calcium Re-uptake by cytoplasmic
  reticulum, thus sustained skeletal muscle
  contraction.
• Malignant Hyperthermia risk not clear, assume
  risk.
• SCh-BAD!, Hyperkalemia, worse muscle contraction
• NDMR-works normally

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Multiple Sclerosis

• Demylelination of corticospinal tracts in brain
• Cause possibly autoimmune
• Peripheral nervous system NOT affected
• Increased temperature worsens symptoms
• Unpredictable response to muscle relaxants
• SCh- possible Hyperkalemia
• NDMR ? or? response

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Guillain-Barre ( Acute Idiopathic Polyneuritis)

• Demyelination of peripheral nerves
• Cause possibly autoimmune
• Sudden onset weakness in legs spreads cephalad
• Autonomic dysfunction. Wide vital sign swings
• Complete recovery usually within weeks
• SCh- Hyperkalemia
• NDMR-Prolonged response

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Amyotropic Lateral Sclerosis ALS

• UPPER and LOWER motor neuron dysfunction
• Atrophy of skeletal muscles
• Cause viral,toxin,immune dysfunction,trauma, DNA
• SCh- Hyperkalemia
• NDMR-Prolonged response

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Spinal Cord Transection

• Up-regulation after 48-72 hrs ,Risks for 3-6
  months
• ACUTE SCh- effective, safe within first 24
  hrs NDMR- effective, safe
• CHRONIC SCh-Hyperkalemia risk first 6 months
  NDMR- effective, safe

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Burn Injuries

• Up-regulation extrajuctional cholinergic
  receptors
• SCh- Hyperkalemia Peak 10-50 days
• NDMR- 3 fold resistance (gt30 TBSA) Onset
  10 days Peak 40 days Decline 60
  days

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Parkinsons Disease (Paralysis Agitans)

• Degeneration of central nervous system
• Dopamine depletion in basal ganglia
• SS-rigidity to tremors d/t ? inhibition
  extrapyramidal motor impulses
• No alteration in muscle relaxant action

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Key Points For Today
?Depolarizers are AGONISTIC at neuro-muscular
junction
? Non-Depolarizers are ANTAGONISTIC at
neuro-muscular junc.
? Head lift for 5 sec.s MOST indicative of
adequate muscle
relaxant reversal
? Myasthenia Gravis- DECRESED ACh RECEPTORS
? Myasthenic Syndrome or Eaton-Lambert Disease-
Autoimmune, DECREASED ACh molecules
? Differentiating Myasthenic Crisis(?ACh ) from
Cholinergic Crisis(? ACh) , Give Edrophonium
1-10 mg IV. ImprovementMyasthenic Crisis
?AVOID SCh with Muscular Dystrophies and
Myotonias
?Avoid SCh with Spinal Cord and Burn injuries
?Avoid SCh with ALL demyelinating diseases